Add list and detail serializer with tests for shifting module

[GeekGawd]

Proposed Changes

• Add list and detail serializer with tests for shifting module
• Add tests and comments

Associated Issue

• Fixes shifting.py in https://github.com/coronasafe/care_fe/issues/5492

Merge Checklist

• [x] Tests added/fixed
• [x] Linting Complete

Only PR's with test cases included and passing lint and test pipelines will be reviewed

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